The efforts of our research have been devoted to the physiochemical and molecular characterization of monoclonal immunoglobulins. The purpose of these studies is to gain an insight into (1) the genetic basis of antibody synthesis, (2) the relationship between the genetic defects found in heavy chain disease immunoglobulins and the origins of these plasma cell dyscrasias and (3) the nature of the antibody-combining sites and the molecular basis of antibody specificity. We are currently defining the primary structure of three immunoglobulins: IgG GAR, a lambda-type Bence-Jones protein(WHITE), and IgG-Sm. The IgG GAR is a myeloma protein of the IgG-2 subclass containing lambda-type L-chains and has antibody-like activity for riboflavin. IgG-Sm contains lambda-type L-chains which have an internal deletion of 81 residues and we now are presently analyzing the structure of the gamma chain. Protein WHITE contains a substantial amount of carbohydrate; we will define the sequence and point of carbohydrate attachment.